One of the most impressive testimonials to sea life anywhere opened in 1996 in Barcelona's Port Vell, a 10-minute walk from the bottom of La Rambla. One of the largest aquariums in Europe, it contains 21 glass tanks positioned along either side of a wide curving corridor. Each tank depicts a different marine habitat, containing multicolored fish and corals, seagoing worms, and sharks. The highlight is a huge "oceanarium" representative of the Mediterranean as a self-sustaining ecosystem. View it from the inside of a glass tunnel running along its entire length, with fish, eels, and sharks swimming all around you. Kids can let off some steam in the Explora section, a collection of touchy-feely educational exhibits on Catalonia's Costa Brava and Ebro Delta.